The invention disclosed herein pertains to a device for turning threaded caps onto the threaded necks of containers with a controlled maximum torsional force.
Capping devices for applying threaded caps on the necks of prethreaded containers are generally well known. To assure that the threaded cap is not applied too tightly to the container, most advanced capping devices incorporate a magnetic clutch comprised of a hysteresis ring composed of low magnetic reluctance material, such as that known by the trademark Hysterloy, fastened to a rotationally driven part and a plurality of permanent magnets disposed within a circle within the ring and magnetically coupled to a member that engages with the cap such that when a certain torsional force is reached the hysteresis ring slips relative to the magnets to thereby limit the transmitted torsional force that is applied to the cap. A hysteresis clutch is disclosed in U.S. Pat. No. 4,485,609, for example.
In some production lines using prior art capping devices, containers with caps loosely applied are loaded onto a conveyor, such as a rotating turntable or linear conveyor, for being transported while the cap of the container is engaged by a cap tightener device which moves synchronously with the container. Typically, the device is mounted to a shaft which is driven rotationally for imparting a torsional force to the device for it to tighten the cap. A disadvantage of this arrangement is that every cap tightener device is mounted on a shaft which must be driven rotationally for the cap tightener to turn the cap and besides a camming mechanism is required for lowering and raising the rotating shaft and the device to grip the cap and to withdraw it from the cap. This results in an unduly complicated and expensive capping machine.